1. Field of the Invention
The present invention relates to a capacitive touch panel and a method for manufacturing the same, and more particularly to a capacitive touch panel and a method for manufacturing the same capable of reducing material cost and accelerating production speed.
2. Description of the Related Art
With reference to FIG. 7A, a conventional capacitive touch panel is shown. The conventional capacitive touch panel has/comprises multiple first-axis sensing lines L1 (along X axis) and multiple second-axis sensing lines L2 (along Y axis) formed on one surface of a printed circuit board (PCB) 70 and intersecting one another. With reference to FIG. 8, multiple conductive traces 100 and a control circuit are formed on the other opposite surface of the PCB 70. The control circuit has a controller 110. The controller 110 has multiple pins, and each pin is soldered to one end of a corresponding conductive trace 100. Each of the first-axis sensing lines L1 and the second-axis sensing lines L2 has a conductive via P formed at an end thereof and penetrating through the two opposite surfaces of the PCB 70 to connect with one of the conductive traces 100. Hence, the controller 110 can transmit driving signals to and receive sensing signals from the first-axis sensing lines L1 and the second-axis sensing lines L2 through the corresponding conductive traces 100 and conductive vias P.
As the foregoing capacitive touch panel must have the first-axis sensing lines L1 and the second-axis sensing lines L2 formed on the same surface of the PCB 70, the most direct approach is to adopt a multilayer circuit board. With reference to FIG. 7B, an inner connection line 82 is connected between two of multiple second-axis sensing units 81 of each second-axis sensing line L2 such that the first-axis sensing units of the first-axis sensing lines L1 and the second-axis sensing units of the second-axis sensing lines L2 are formed on the same surface of the multilayer circuit board. However, the cost of multilayer circuit board is high, and a multilayer circuit board is thicker than a double-layer circuit board. To reduce thickness of the capacitive touch panel, a capacitive touch panel with a double-layer circuit board is developed. The double-layer circuit board has the first-axis sensing lines L1 and the second-axis sensing lines L2 formed on the same surface thereof. With reference to FIG. 9A, a manufacturing method of the capacitive touch panel has the following steps.
Provide a double-layer substrate 70′ having two opposite surfaces.
Form multiple first-axis sensing lines L1 arranged in parallel rows along a first-axis (X) direction on a surface of the double-layer substrate 70′, multiple second-axis sensing units 81 arranged in parallel columns along a second-axis (Y) direction and aligned in each row located between adjacent two of the first-axis sensing lines L1, and multiple connection circuits 100 on the other opposite surface of the double-layer substrate 70′.
Fully coat a layer of green paint 90 on the surface of the double-layer substrate 70′ having the first-axis sensing lines L1 and the second-axis sensing units 81 thereon as shown in FIG. 9B, except that two ends 811 of each second-axis sensing unit 81 are left uncoated.
Print multiple carbon conductors 82′ on the green paint 90 as shown in FIG. 9C. Each carbon conductor 82′ is connected between two adjacent ends 811 of adjacent two of the second-axis sensing units 81 so that the second-axis sensing units 81 aligned in the second-axis direction form multiple second-axis sensing lines L2.
Solder a quad flat no leads (QFN) controller 110 onto the surface of the double-layer substrate 70′ having the connection circuits 100 to connect with one end of each connection circuit 100 for the QFN controller 110 to connect to the first-axis sensing lines L1 and the second-axis sensing lines L2 through the connection circuits 100. In general, multiple conductive vias P are formed through the double-layer substrate 70 and corresponding to locations of the first-axis sensing lines L1 and the second-axis sensing lines L2. The connection circuits 100 are connect to the first-axis sensing lines L1 or the second-axis sensing lines L2 through the conductive vias P.
In the foregoing conventional capacitive touch panel, the first-axis sensing lines and the second-axis sensing lines are formed on one surface of the double-layer circuit board by leaving the two ends of each second-axis sensing unit in each second-axis sensing line uncoated by the green paint, and then connecting the second-axis sensing units with the carbon conductors to form the second-axis sensing line. As the carbon conductors and the first-axis sensing lines are insulated by green paint between them, an electrically insulating structure of bridging conductor is completed. As long as the first-axis sensing lines and the second-axis sensing lines can be formed on the double-layer substrate, such type of capacitive touch panel should be thinner than those having multilayer circuit board. However, such conventional capacitive touch panel requires an additional manufacturing process (printing carbon conductors) besides the electroplating process for regular PCBs. As printing the carbon conductors involves high material cost and longer production time arising from complicated manufacturing processes, such as baking, hardening and the like, such conventional capacitive touch panel is not ideal for the sake of cost consideration.
Even though a conductive via P can be formed through one end of each of the first-axis sensing lines L1 and the second-axis sensing lines L2 on the double-layer substrate 70′ and connected to a corresponding connection circuit 100, the second-axis sensing units having the corresponding conductive vias formed therethrough and connecting with the conductive vias to form a corresponding second-axis sensing line has the following limitations.
1. As the current controllers (hereafter called QFN controller) mostly pertain to the integrated circuits (IC) fabricated by a QFN packaging process, after a QFN controller is soldered on a circuit board, a bottom of a package of the QFN controller is almost flatly attached on a surface of the circuit board, and usually occupies an area covering several second-axis sensing units. Hence, there is almost no space between the bottom of the QFN controller and the surface of the circuit board available for the formation of the conductive vias except the area not occupied by the bottom of the QFN controller.
2. Automatic routing software is not applicable: As the carbon conductor connected between any adjacent two of the second-axis sensing units is formed on the surface having the connection circuits, the original connection paths between the connection circuits and the pins of the controller are subject to change, and also the area not occupied by the QFN controller needs to be identified. Accordingly, manual routing is needed instead and the time and complication for the routing design certainly increases.